Make all methods on Duration const

Author: pitdicker

src/duration.rs

@@ -16,6 +16,8 @@ use core::{fmt, i64};
 #[cfg(feature = "std")]
 use std::error::Error;
 
+use crate::{expect, try_opt};
+
 #[cfg(feature = "rkyv")]
 use rkyv::{Archive, Deserialize, Serialize};
 
@@ -75,88 +77,88 @@ impl Duration {
     /// Panics when the duration is out of bounds.
     #[inline]
     #[must_use]
-    pub fn weeks(weeks: i64) -> Duration {
-        Duration::try_weeks(weeks).expect("Duration::weeks out of bounds")
+    pub const fn weeks(weeks: i64) -> Duration {
+        expect!(Duration::try_weeks(weeks), "Duration::weeks out of bounds")
     }
 
     /// Makes a new `Duration` with given number of weeks.
     /// Equivalent to `Duration::seconds(weeks * 7 * 24 * 60 * 60)` with overflow checks.
     /// Returns `None` when the duration is out of bounds.
     #[inline]
-    pub fn try_weeks(weeks: i64) -> Option<Duration> {
-        weeks.checked_mul(SECS_PER_WEEK).and_then(Duration::try_seconds)
+    pub const fn try_weeks(weeks: i64) -> Option<Duration> {
+        Duration::try_seconds(try_opt!(weeks.checked_mul(SECS_PER_WEEK)))
     }
 
     /// Makes a new `Duration` with given number of days.
     /// Equivalent to `Duration::seconds(days * 24 * 60 * 60)` with overflow checks.
     /// Panics when the duration is out of bounds.
     #[inline]
     #[must_use]
-    pub fn days(days: i64) -> Duration {
-        Duration::try_days(days).expect("Duration::days out of bounds")
+    pub const fn days(days: i64) -> Duration {
+        expect!(Duration::try_days(days), "Duration::days out of bounds")
     }
 
     /// Makes a new `Duration` with given number of days.
     /// Equivalent to `Duration::seconds(days * 24 * 60 * 60)` with overflow checks.
     /// Returns `None` when the duration is out of bounds.
     #[inline]
-    pub fn try_days(days: i64) -> Option<Duration> {
-        days.checked_mul(SECS_PER_DAY).and_then(Duration::try_seconds)
+    pub const fn try_days(days: i64) -> Option<Duration> {
+        Duration::try_seconds(try_opt!(days.checked_mul(SECS_PER_DAY)))
     }
 
     /// Makes a new `Duration` with given number of hours.
     /// Equivalent to `Duration::seconds(hours * 60 * 60)` with overflow checks.
     /// Panics when the duration is out of bounds.
     #[inline]
     #[must_use]
-    pub fn hours(hours: i64) -> Duration {
-        Duration::try_hours(hours).expect("Duration::hours ouf of bounds")
+    pub const fn hours(hours: i64) -> Duration {
+        expect!(Duration::try_hours(hours), "Duration::hours ouf of bounds")
     }
 
     /// Makes a new `Duration` with given number of hours.
     /// Equivalent to `Duration::seconds(hours * 60 * 60)` with overflow checks.
     /// Returns `None` when the duration is out of bounds.
     #[inline]
-    pub fn try_hours(hours: i64) -> Option<Duration> {
-        hours.checked_mul(SECS_PER_HOUR).and_then(Duration::try_seconds)
+    pub const fn try_hours(hours: i64) -> Option<Duration> {
+        Duration::try_seconds(try_opt!(hours.checked_mul(SECS_PER_HOUR)))
     }
 
     /// Makes a new `Duration` with given number of minutes.
     /// Equivalent to `Duration::seconds(minutes * 60)` with overflow checks.
     /// Panics when the duration is out of bounds.
     #[inline]
     #[must_use]
-    pub fn minutes(minutes: i64) -> Duration {
-        Duration::try_minutes(minutes).expect("Duration::minutes out of bounds")
+    pub const fn minutes(minutes: i64) -> Duration {
+        expect!(Duration::try_minutes(minutes), "Duration::minutes out of bounds")
     }
 
     /// Makes a new `Duration` with given number of minutes.
     /// Equivalent to `Duration::seconds(minutes * 60)` with overflow checks.
     /// Returns `None` when the duration is out of bounds.
     #[inline]
-    pub fn try_minutes(minutes: i64) -> Option<Duration> {
-        minutes.checked_mul(SECS_PER_MINUTE).and_then(Duration::try_seconds)
+    pub const fn try_minutes(minutes: i64) -> Option<Duration> {
+        Duration::try_seconds(try_opt!(minutes.checked_mul(SECS_PER_MINUTE)))
     }
 
     /// Makes a new `Duration` with given number of seconds.
     /// Panics when the duration is more than `i64::MAX` milliseconds
     /// or less than `i64::MIN` milliseconds.
     #[inline]
     #[must_use]
-    pub fn seconds(seconds: i64) -> Duration {
-        Duration::try_seconds(seconds).expect("Duration::seconds out of bounds")
+    pub const fn seconds(seconds: i64) -> Duration {
+        expect!(Duration::try_seconds(seconds), "Duration::seconds out of bounds")
     }
 
     /// Makes a new `Duration` with given number of seconds.
     /// Returns `None` when the duration is more than `i64::MAX` milliseconds
     /// or less than `i64::MIN` milliseconds.
     #[inline]
-    pub fn try_seconds(seconds: i64) -> Option<Duration> {
+    pub const fn try_seconds(seconds: i64) -> Option<Duration> {
         let d = Duration { secs: seconds, nanos: 0 };
-        if d < MIN || d > MAX {
-            return None;
+        match d.out_of_bounds() {
+            true => None,
+            false => Some(d),
         }
-        Some(d)
     }
 
     /// Makes a new `Duration` with given number of milliseconds.
@@ -253,7 +255,7 @@ impl Duration {
 
     /// Add two durations, returning `None` if overflow occurred.
     #[must_use]
-    pub fn checked_add(&self, rhs: &Duration) -> Option<Duration> {
+    pub const fn checked_add(&self, rhs: &Duration) -> Option<Duration> {
         let mut secs = try_opt!(self.secs.checked_add(rhs.secs));
         let mut nanos = self.nanos + rhs.nanos;
         if nanos >= NANOS_PER_SEC {
@@ -263,16 +265,15 @@ impl Duration {
         let d = Duration { secs, nanos };
         // Even if d is within the bounds of i64 seconds,
         // it might still overflow i64 milliseconds.
-        if d < MIN || d > MAX {
-            None
-        } else {
-            Some(d)
+        match d.out_of_bounds() {
+            true => None,
+            false => Some(d),
         }
     }
 
     /// Subtract two durations, returning `None` if overflow occurred.
     #[must_use]
-    pub fn checked_sub(&self, rhs: &Duration) -> Option<Duration> {
+    pub const fn checked_sub(&self, rhs: &Duration) -> Option<Duration> {
         let mut secs = try_opt!(self.secs.checked_sub(rhs.secs));
         let mut nanos = self.nanos - rhs.nanos;
         if nanos < 0 {
@@ -282,10 +283,9 @@ impl Duration {
         let d = Duration { secs, nanos };
         // Even if d is within the bounds of i64 seconds,
         // it might still overflow i64 milliseconds.
-        if d < MIN || d > MAX {
-            None
-        } else {
-            Some(d)
+        match d.out_of_bounds() {
+            true => None,
+            false => Some(d),
         }
     }
 
@@ -327,13 +327,13 @@ impl Duration {
     ///
     /// This function errors when original duration is larger than the maximum
     /// value supported for this type.
-    pub fn from_std(duration: StdDuration) -> Result<Duration, OutOfRangeError> {
+    pub const fn from_std(duration: StdDuration) -> Result<Duration, OutOfRangeError> {
         // We need to check secs as u64 before coercing to i64
         if duration.as_secs() > MAX.secs as u64 {
             return Err(OutOfRangeError(()));
         }
         let d = Duration { secs: duration.as_secs() as i64, nanos: duration.subsec_nanos() as i32 };
-        if d > MAX {
+        if d.out_of_bounds() {
             return Err(OutOfRangeError(()));
         }
         Ok(d)
@@ -343,12 +343,21 @@ impl Duration {
     ///
     /// This function errors when duration is less than zero. As standard
     /// library implementation is limited to non-negative values.
+    // TODO: make this method const once our MSRV is 1.58+
     pub fn to_std(&self) -> Result<StdDuration, OutOfRangeError> {
         if self.secs < 0 {
             return Err(OutOfRangeError(()));
         }
         Ok(StdDuration::new(self.secs as u64, self.nanos as u32))
     }
+
+    /// Returns `true` if d < MIN || d > MAX
+    const fn out_of_bounds(&self) -> bool {
+        self.secs < MIN.secs
+            || self.secs > MAX.secs
+            || (self.secs == MAX.secs && self.nanos > MAX.nanos)
+            || (self.secs == MIN.secs && self.nanos < MIN.nanos)
+    }
 }
 
 impl Neg for Duration {